Outcome of single- versus two-visit root canal retreatment in teeth with periapical lesions: A randomized clinical trial Fulya Karaoğlan | Seniha Miçooğulları Kurt | Mehmet Kemal Çalışkan © 2022 International Endodontic Journal. Published by John Wiley & Sons Ltd. Department of Endodontics, Faculty of Dentistry, Ege University, İzmir, Turkey Correspondence Seniha Miçooğulları Kurt, Department of Endodontology, School of Dentistry, Ege University, 35040, Bornova, İzmir, Turkey. Email: [email protected] Abstract Aim: The aim of the study was to evaluate the clinical and radiographic outcome of single-visit root canal retreatment and compare the results with conventional twovisit root canal retreatment as control group. Methodology: One hundred root canal-treated, single-rooted asymptomatic teeth with periapical lesion were retreated by one operator. Fifty of the teeth were randomly assigned to the single-visit group and the others were treated in two visits. In both groups, root canal filling material was removed, and re-instrumentation of the root canal was performed using step-back technique with hand files using 2.5% NaOCl and 5% EDTA as irrigants. In the single-visit group, 5 ml 2% chlorhexidine (CHX) were applied as the final irrigation and in the two-visit group, calcium hydroxide paste was placed into the root canal as an interappointment dressing. All root canal obturations were performed with lateral compaction. All patients were followed up for 24months. The success was determined depending on both healed and healing cases. The chi-square or Fisher's exact test was used to analyse the differences between the groups for success rates and the factors affecting the outcome. Results: The recall rate was 89 (89%). At 24months, 39 teeth (88.6%) were considered as healed, three teeth (6.8%) as healing, and two teeth (4.5%) were identified as failed in the single-visit group, while in the two-visit group 39 teeth (86.7%) had healed, two teeth (4.4%) were scored as healing, and four teeth (8.9%) as failed. There was no statistically significant difference in the success rates between the two groups (p>.05). Size of the lesion and the preoperative length of root canal filling had a statistically significant impact on the outcome (p.05). Representative periapical radiographs of two cases belonging to single and two-visit groups are shown in Figure 2. Failure was observed in two teeth (4.5%) treated in a single visit, one of which was extracted with a suspect of vertical root fracture and the other one was clinically asymptomatic, but the PAI score had not changed during the follow-up periods. On the other hand, the failure rate was 8.9% (four teeth) in the two-visit group, one of which had a sinus tract, and the other three teeth were clinically asymptomatic, but the PAI score had not reduced. In teeth with large periapical lesions, the success rate was significantly lower than teeth with small lesions (p35 46 21 (47.7) 25 (55.6) Gender Female 60 32 (72.7) 28 (62.2) 1.118 .290 Male 29 12 (27.3) 17 (37.8) Location of tooth Maxilla 63 34 (77.3) 29 (64.4) 1.77 .183 Mandibula 26 10 (22.7) 16 (35.6) Preoperative lesion size (mm) 2–5.9 50 25 (56.8) 25(55.6) .014 .904 6–10 39 19 (43.2) 20 (44.4) Preoperative length of root filling Short 45 25 (56.8) 20 (44.4) 1.945 .378 Adequate 40 18 (40.9) 22 (48.9) Long 4 1 (2.3) 3 (6.7) Preoperative density of root filling Poor 63 31 (70.5) 32 (71.1) .005 .946 Good 26 13 (29.5) 13 (28.9) Intra-operative Post Absent 74 36 (81.8) 38 (84.4) .109 .741 Present 15 8 (18.2) 7 (15.6) Coronal restoration Composite 62 27 (61.4) 35 (77.8) 2.836 .092 Crown 27 17 (38.6) 10 (22.2) TABLE 1 Distribution of the relevant preoperative and intra-operative factors in both treatment groups TABLE 2 Proportion of teeth healed, healing and fKARAOĞLAN et al. 839 oval-shaped root canals (Peters et al., 2001). Considering the root canal morphologies and apical diameter of the teeth included in the current study, hand files were used to remove the existing root canal fillings and for reinstrumentation of the root canals. The outcome of the teeth that require root canal retreatment is challenging, and the success rate of single-visit root canal retreatment may differ from the primary root canal treatment due to the previous root canal filling material that makes the removal of the bacteria and inflammatory mediators difficult (Imura et al., 2000). Additionally, it has been reported that the diversity of microorganisms in root canal treated teeth is different from that in primarily infected root canals, and that resistant microorganisms such FIGURE 2 Representative periapical radiographs of (a, b) single-visit root canal retreatment case and (c, d) two-visit root canal retreatment case. (a, c) Preoperative radiographs and (b, d) 24-month follow-up radiographs showing resolution of the periapical lesions. (a) (b) (c) (d) n Healed n (%) Healing n (%) Failure n (%) p value Preoperative factors Preoperative lesion size (mm) 2–5.9 50 50 (100) 0 (0) 0 (0) <.001 6–10 39 28 (71.8) 5 (12.8) 6 (15.4) Preoperative length of root filling Short 45 41 (91.1) 1 (2.2) 3 (6.7) .025 Adequate 40 35 (87.5) 4 (10) 1 (2.5) Long 4 2 (50) 0 (0) 2 (50) TABLE 3 Effect of preoperative factors on the outcome of root canal retreatment 13652591, 2022, 8, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/iej.13758 by Ege University, Wiley Online Library on [28/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 840 | ONE- OR TWO- VISITS ROOT CANAL RETREATMENT as E. faecalis may play an important role in cases requiring root canal retreatment (Gomes et al., 2008; Siqueira Jr & Rôcas, 2008; Sundqvist et al., 1998). To ensure optimum disinfection especially in single-visit root canal retreatment (Siqueira Jr & Rôças,  2011), it is recommended to irrigate the root canals with EDTA and NaOCl, and then to use CHX, a bisguanid agent with broad antimicrobial spectrum effective against anaerobic and aerobic bacteria, fungi, and lipophilic viruses, as the final irrigation (Zamany et al., 2003; Zehnder, 2006). In the light of this information, in the single-visit group of the present study, root canals were irrigated with 2% CHX solution kept it in the root canal for 2 min before obturation to ensure contact with the canal walls. CH was used as an intracanal medicament in the two-visit control group. In the present study, at the 24th month recall, 88.6% of the cases in the single-visit group and 86.7% in the twovisit group were found to be completely healed, and the healing rate was 6.8% and 4.4% in the single-visit and twovisit groups, respectively. Quite high cumulative success rates were found for both groups (single-visit 95.4%; twovisit 91.1%) including healing cases which did not show any clinical symptoms during the 24-month follow-up period with radiographical reduction in size of the lesions accepted as success. In similar studies examining the outcome of single or two-visit root canal retreatments, He et al. (2017), examined the success of two-visit root canal retreatments in first molars and the cumulative success rate were determined as 90.4%. Zandi et al. (2019) compared the use of NaOCl and CHX in multi-visit root canal retreatment and reported a complete healing rate of 81% in the NaOCl group and 82% in the CHX group. Zhang et al. (2021) reported that 75.9% complete healing occurred in their study, in which they evaluated periapical lesions healing using CBCT at the 4th year after multi-visit root canal retreatment. On the other hand, Ashraf et al. (2007) evaluated the success rates of root canal retreatments in a single visit and reported that asymptomatic teeth can be retreated in single visit with high success rates (84.9%). Additionally, Eyuboglu et al. (2017) reported a high success rate (90.4%) of retreatments performed in single-visit in teeth with periapical lesions. Although CHX irrigation is recommended for ensuring optimum disinfection especially in single-visit root canal retreatment (Siqueira Jr & Rôças, 2011), CHX was not used as the final irrigation in any of the above-mentioned studies. However, we have utilized CHX in the single-visit retreatment group in present investigation, which may have a positive effect on disinfection of the root canals. Additionally, in the present study, only the single-rooted teeth that were diagnosed as asymptomatic apical periodontitis were included. High success rates of both groups of the present study can be explained by the exclusion of the multi rooted teeth with a more complex root canal anatomy, inclusion of asymptomatic teeth and using CHX in addition to adequate biomechanical procedures to increase the antimicrobial effect and the success of one-visit root canal retreatment. In the current study, the effect of patients' age and gender on the success were not evaluated due to previously it was reported that these factors had no effect on the success of root canal retreatment (Ng et al.,  2011; Zhang et al., 2021). The preoperative lesion size and apical level of initial root canal filling were evaluated and affected the outcome of root canal retreatment. In recent years, although some prospective studies have emphasized that there are significantly higher bacterial counts in large lesions than in small ones (Zandi et al.,  2019), it has been reported that lesion size has no effect on the success of treatment (He et al., 2017; Zandi et al., 2019; Zhang et al., 2021). On the other hand, similar to the current study, it has been stated that large lesions reduce the chance of success (Barone et al.,  2010; Bergenholtz et al.,  1979; Calıskan,  2005; Eyuboglu et al.,  2017; Ng et al.,  2011; Sjögren et al.,  1990; Sundqvist et al.,  1998) and this result could be attributed to the high bacterial diversity of large periapical lesions, which adversely affected biological healing (Sundqvist,  1976). In the literature, the success rates of teeth with periapical lesions larger than 5mm are reported to be between 38 and 80% (Calıskan, 2005; Eyuboglu et al., 2017; Sjögren et al., 1990). However, in most of these studies, an upper limit for large periapical has not been reported. Sjögren et al.  (1990) reported a 38% success rate after root canal treatment in teeth with large periapical lesions. Although the number of teeth with periapical lesions larger than 5mm evaluated in this study was quite low (13 teeth), and an upper limit was not specified for lesion sizes, this dramatically low success rate (38%) has been a reference to researchers reporting a higher success rate in endodontic surgery compared to root canal retreatment (Danin et al., 1996). Only Calıskan (2005) reported an upper limit (11mm) for large periapical lesions, and after 2- to 8-year follow-up period they reported a 73.5% success rate which was lower than the success rate for teeth with small lesions. While there are prospective studies reporting that the apical level of the root canal filling has no effect on the success (Al-Nuaimi et al.,  2017; Sundqvist et al.,  1998; Zhang et al., 2021), there are also studies reporting that it does (de Chevigny et al., 2008; Farzaneh et al., 2004; Ng et al., 2011). Zandi et al. (2019) reported a higher success rate when the length of the root canal filling could be improved during retreatment. Moreover, it is reported that the success of root canal retreatment decreases for every 1mm left without instrumentation in the apical terminus (Ng et al., 2011). On the other hand, Olcay et al. (2019) reported that the initial root canal filling level did not 13652591, 2022, 8, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/iej.13758 by Ege University, Wiley Online Library on [28/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License | KARAOĞLAN et al. 841 have a significant effect on the success rate of root canal retreatment. However, in the current study, the statistical analysis showed that the success rate of root canal retreatment was significantly reduced in teeth with initially overextended root fillings. Under clinical conditions although radiographic examination demonstrates the absence of any residual filling material, bacteria remaining in the apical region of the root canal and residual extraradicular infection can cause persistent periapical inflammation and reduce the success rate of the root canal retreatment (Fukushima et al., 1990) since microorganisms in periradicular tissues are unachievable by root canal disinfection process (Siqueira Jr,  2001). It should be noted that the number of overextended cases is quite low in the current study. Therefore, clinically it would not be accurate to generalize this finding for all retreatment cases and the inclusion of teeth with a small number of overextended root canal fillings may be a limitation of this study. Additionally, since there were no studies comparing the outcome of single- and multiple-visit root canal retreatment, the data from two separate published studies [50.7% for single visit (Ashraf et al., 2007), and 81.6% for two visits (Ng et al., 2011)] were used for the power analysis. The calculation was performed for the ability to detect differences greater than 30% between the 1-visit and 2-visit treatments, and a total of 100 patients, containing 50 patients in each group were utilized according to the power calculation. Even though our sample size was comparable with high-quality clinical studies of a similar nature (Miçooğullari Kurt & Calıskan,  2018; Molander et al., 2007; Peters & Wesselink, 2002; Zandi et al., 2019), a larger sample size may be more appropriate to detect the significance of a small difference between the groups (Sakpal, 2010). Nevertheless, this limitation of the present study will be prevailed by future randomized controlled trials with larger sample sizes and will help to provide a sound conclusion about the effects of the number of visits on the root canal retreatment outcome. CONCLUSION Within the limitations of the present study, similar success rates were observed in single-visit (88.6%) and twovisit (86.7%) root canal retreatment in asymptomatic teeth with periapical lesions. The size of periapical lesion and initial apical level of root canal filling affected the outcome of root canal retreatment. ACKNOWLEDGEMENTS The authors would like to thank Prof. Dr. Pelin Güneri and Prof. Dr. Michael Hulsmann for their valuable contributions of the study. CONFLICT OF INTEREST The authors declare that they have no conflict of interest. ETHICAL APPROVAL This clinical study was carried out under the approval of The Ethics Committee of Ege University, School of Medicine and in accordance with the principles of Helsinki (version 2008). AUTHOR CONTRIBUTIONS Fulya Karaoğlan: Conceptualization, Methodology, Investigation, Writing- Original draft preparation. Seniha Miçooğulları Kurt: Conseptualization, Data curation, Writing- Reviewing and Editing. Mehmet Kemal Çalışkan: Conceptualization, Methodology, Supervision, Project administration DATA AVAILABILITY STATEMENT Data available on request from the authors ORCID Seniha Miçooğulları Kurt https://orcid. org/0000-0001-7843-5686 Mehmet Kemal Çalışkan https://orcid. org/0000-0002-6714-4282 REFERENCES Al-Nuaimi, N., Patel, S., Austin, R.S. & Mannocci, F. (2017) A prospective study assessing the effect of coronal tooth structure loss on the outcome of root canal retreatment. International Endodontic Journal, 50, 1143–1147. Ashraf, H., Milani, A.S. & Asadi, S.S. 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How to cite this article: Karaoğlan, F., Miçooğulları Kurt, S. & Çalışkan, M.K. (2022) Outcome of single- versus two-visit root canal retreatment in teeth with periapical lesions: A randomized clinical trial. International Endodontic Journal, 55, 833–843.